Antenna device

ABSTRACT

Linear elements  101   a  to  101   d  are conductors, which have the element length equivalent to half a wavelength, have been placed so that they may draw a diamond shape. Delay elements  102   a  and  102   b  are bent conductors, which have a total length equivalent to one fourth wavelength and a length L 2  equivalent to one eighth. The linear elements  101   a  and  101   c  are connected one another via the delay element  102   a , while the linear elements  101   b  and  101   d  are connected one another via the delay element  102   b . A feeding section  103  is connected to each of the ends of the linear elements  101   a  and  101   b  for feeding power to them. Between the tips of the linear elements  101   c  and  101   d , a gap with a length L 3  is left. A reflector  104  has been placed at a distance h from a diamond-shape antenna with delay elements along the −Z axis, the distance h being equivalent to 0.42 wavelength. This achieves the antenna device, which may be suitably mounted on any of small wireless apparatuses and form a primary beam, of which horizontally-polarized wave or vertically-polarized wave tilts toward the horizontal direction.

TECHNICAL FIELD

The present invention relates to an antenna device used in mobilecommunications, which may be suitably applied to, for example, fixedwireless apparatuses and wireless terminals configured in a wireless LANsystem.

BACKGROUND ART

In wideband wireless communications through, for example, a wireless LANsystem, such a problem has arisen that the quality of transmission isdeteriorated due to multi-path fading or shadowing, especially in indoorapplications. For this reason, it is required to develop a directiveantenna mounted on a wireless apparatus capable of being controlled sothat a primary beam radiated from it may advance toward any direction tomaintain the quality of transmission at a moderate level even in a poorradio-wave propagation environment affected by multi-path fading orshadowing.

In addition, it is further required that an antenna, which is mounted ona notebook-PC type of terminal wireless apparatus for using on a desk oron a fixed type of wireless apparatus attached to a ceiling, has aplanar structure because of these apparatuses' configurations. It isalso required that the elevation angle of a primary beam tilts towardthe horizontal direction from the vertical direction relative to theantenna plane.

As an example of a sector antenna providing such a radiationcharacteristic, a Yagi-Uda slot array planar multi-sector antenna hasbeen disclosed in Journal of the Institute of Electronics, Informationand Communication Engineers of Japan (IEICE) ((B) Vol. J85-B, No. 9, pp.1633-1643, 2002). In the following paragraphs, the sector antenna isbriefly described.

FIG. 1 is a plan view showing the configuration of a conventional sectorantenna. As shown in the figure, each of slot arrays 11 a to 11 f hasfive-element slots vertically placed. The sector antenna has aconfiguration, in which the slot arrays 11 a to 11 f are placed in aradial pattern, drawing a circle. The primary beam radiated from each(for example, 11 a alone) of the slot arrays, of which elevation angle θtilts at any angle between 45° and 60° relative to the vertical plane,advances toward a horizontal plane. By placing these slot arrays at aninterval of 60° relative to the horizontal plane (XY plane) andselectively feeding power to any of slot arrays 11 a to 11 f, thedirectivity of the primary beam can be switched among the sectors, eachhaving an angle of 60° (360°0.6) The dimension of the sector antenna is198 mm (equivalent to 3.3 wavelength) in diameter L17 and 30790 mm² inarea, assuming that the operating frequency of the antenna device is,for example, 5 GHz.

As another type of antenna, an end-open diamond-shape antenna, has beendisclosed in the patent document JP-A No. 355030/1999 and Journal of theInstitute of Electronics, Information and Communication Engineers ofJapan (IEICE) ((B) Vol. J82-B, No. 10, pp. 1915 to 1922, 1999). FIG. 2is a plan view showing the configuration of a conventional diamond-shapeantenna. As shown in the figure, linear elements 21 and 22, each ofwhich has a length equivalent to one wavelength of the operatingfrequency and has been bent at its center at a given angle, are placedso that they draw a diamond shape with a gap left between their apexes.In the case of this type of antenna, by feeding power at a feeding point23, the primary beam advancing along a Z-axis perpendicular to theantenna plane (XY plane), may be obtained.

The conventional Yagi-Uda slot array planar multi-sector antennaaforementioned, however, has such a problem that it is difficult tomount on small size wireless apparatuses because the dimension of itsplane incorporating six sectors is large and furthermore, the sectorsneed to be placed so that they may draw a circle.

Besides, the conventional end-open diamond-shape antenna aforementioned,of which primary beam advances in the direction perpendicular to theantenna plane, thereby does not tilt horizontally, has such a problemthat it may not suitably mounted on the notebook-PC type of wirelessterminal or the fixed wireless apparatus attached to the ceiling.

DISCLOSURE OF INVENTION

An object of the present invention is to provide an antenna device,which may be suitably mounted on any of small wireless apparatuses andforms a primary beam, of which horizontally-polarized wave orvertically-polarized wave tilts toward the horizontal plane.

The object of the present invention aforementioned may be achieved byplacing each of the delay elements at one of the opposite apex pairs anda reflector is inserted at a given distance in parallel to the antennaplane, on which the elements have been placed in the case of theend-open diamond-shape antenna, of which each side has a lengthequivalent to half a wavelength.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing the configuration of a conventional sectorantenna.

FIG. 2 is a view showing the configuration of a conventionaldiamond-shape antenna.

FIG. 3 is a view showing the configuration of an antenna deviceaccording to Embodiment 1 of the present invention.

FIG. 4A is a schematic diagram showing the current distribution of theantenna device according to Embodiment 1 of the present invention.

FIG. 4B is a schematic diagram showing the current distribution of theantenna device according to Embodiment 1 of the present invention.

FIG. 5 is a pattern diagram explaining the operating principle of theantenna device according to the embodiment 1 of the present inventionusing a point source model.

FIG. 6A is a view showing the directivity of the antenna deviceaccording to Embodiment 1 of the present invention.

FIG. 6B is a view showing the directivity of the antenna deviceaccording to Embodiment 1 of the present invention.

FIG. 7 is a view showing the configuration of an antenna deviceaccording to Embodiment 2 of the present invention.

FIG. 8A is a view showing the directivity of the antenna deviceaccording to Embodiment 2 of the present invention.

FIG. 8B is a view showing the directivity of the antenna deviceaccording to Embodiment 2 of the present invention.

FIG. 9 is a view showing the configuration of an antenna deviceaccording to Embodiment 3 of the present invention.

FIG. 10A is a view showing the directivity of the antenna deviceaccording to Embodiment 3 of the present invention.

FIG. 10B is a view showing the directivity of the antenna deviceaccording to Embodiment 3 of the present invention.

FIG. 11 is a view showing the configuration of an antenna deviceaccording to Embodiment 4 of the present invention.

FIG. 12A is a view showing the directivity of the antenna deviceaccording to Embodiment 4 of the present invention.

FIG. 12B is a view showing the directivity of the antenna deviceaccording to Embodiment 4 of the present invention.

FIG. 13 is a view showing the configuration of an antenna deviceaccording to Embodiment 5 of the present invention.

FIG. 14 is a view showing the directivity of the antenna deviceaccording to Embodiment 5 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, preferred embodiments of the present invention re mentioned inreference to accompanying drawings.

Embodiment 1

FIG. 3 is a view showing the configuration of an antenna deviceaccording to an embodiment 1 of the present invention. In the followingparagraphs, the configuration of the antenna device according to theembodiment 1 is mentioned, assuming that the operating frequency of theantenna is 5 GHz.

Linear elements 101 a to 101 d are conductors having an element lengthL1 equivalent to half a wavelength (30 mm) and an element width, forexample, 1 mm. These linear elements 101 a to 101 d are placed so thatthey may draw a diamond shape together as shown in FIG. 3.

In the figure, delay elements 102 a and 102 b are conductors, which havebeen bent at a point equivalent to one eighth wavelength (7.5 mm), havea total length equivalent to one fourth wavelength (15 mm) and anelement width of 1 mm, wherein a length L2 indicates the length of oneof their longitudinal sides. The linear elements 101 a and 101 c areconnected one another via the delay element 102 a, while the linearelements 101 b and 101 d are connected one another via the delay element102 b.

A feeding point 103 is connected to one end of the linear element 101 cand one end of the linear element 101 a for feeding power to them. Notethat a gap of length L3 is left between the tips of the linear elements101 c and 101 d.

The diamond-shape antenna shown in FIG. 3 is composed of the linearelements 101 a to 101 d, the delay elements 102 a and 102 b, and thefeeding point 103.

A reflector 104 is placed at a position on the −Z side, leaving adistance h equivalent to 0.42 wavelength (25 mm) from the plane on whichthe diamond-shape antenna having delay elements is placed. The reflector104 is a square conductor plate with a length of each side almostequivalent to one (60 mm) or more wavelength. In one of the methods forstabilizing the distance h by firmly fixing the diamond-shape antennawith delay elements and the reflector 104, for example, a resin spaceris used to mechanically support them. This method has less influence onantenna performance.

Then, the operating principle of the antenna device having theaforementioned configuration is mentioned in reference to theaccompanying drawings. FIGS. 4A and 4B are schematic diagrams showingthe current distribution on an antenna device according to theembodiment 1 of the present invention.

In FIG. 4A, antenna currents flowing on the linear elements 101 a and101 b are distributed as indicated by arrows 105 a and 105 b. Thedirections of the heads of these arrows suggest that the antennacurrents flowing on the linear elements 101 a and 101 b are in phase.The antenna currents distributed on the linear elements 101 c and 101 dhave values 0s (zero's) when 105 a and 105 b reach their maximum valuesbecause their phases are delayed by one fourth wavelength relative tothose of 105 a and 105 b by means of the delay elements 102 a and 102 bas shown in FIG. 4. Assuming that two elements, the linear elements 101a and 101 b, are paired, the antenna current may be considered to be acomposed vector of arrows 105 a and 105 b, thereby the antenna behavesalmost as a one-wavelength dipole polarized along the Y-axis.

Similarly, in FIG. 4B, the antenna currents flowing on the linearelements 101 c and 101 d are distributed as indicated by arrows 106 aand 106 b. The directions of the arrowheads suggest that the antennacurrents are in phase. Assuming that two elements, the linear elements101 c and 101 d, are paired, the antenna current may be considered to bea composed vector of arrows 106 a and 106 b, thereby the antenna may beregard as a one-wavelength dipole polarized along the Y-axis. Assumingthat no delay elements 102 a and 102 b have incorporated, and the linearelements 101 a and 101 c are connected one another while the linearelements 101 b and 101 d being connected one another, the primary beamadvances along Z-axis and the primary polarized wave is related to theY-axis. This is the operating principle of the conventionaldiamond-shape antenna shown in FIG. 2.

Then, focusing on a vertical X-Z plane, the operating principle of theantenna device, of which delay elements 101 a and 101 b are connectedone another, shown in FIG. 3 is mentioned.

One of models focusing exclusively on the vertical X-Y plane is a pointsource model shown in FIG. 5. FIG. 5 is a pattern view explaining theoperation of the antenna according to the embodiment 1 of the presentinvention using the point source model. A pair of linear elements 101 aand 101 b is modeled as the point source 301, while a pair of 101 c and101 d is modeled as a point source 302. Since the element length of eachof the delay elements 102 a and 102 b is equivalent to one fourthwavelength, the excitation phase at the point source 301 advances fromthat at the point source 302 by 90°.

It is assumed that the point sources 303 and 304 are placed at adistance 2 h (0.84 wavelength: 50 mm) from the point sources 301 and 302to model the effect of the reflector 104. Based on the principle oftransformation, the excitation phases of the point sources 303 and 304may reverse their courses by 180° relative to those of the point sources301 and 302.

Since the position of each point source along the X-axis is assumed tobe the center of each linear element, the interval L4 between the pointsources along the X-axis is equivalent to 0.71 wavelength (42.4 mm).

With four point sources 301 to 304 placed in this way, the arrayradiates the primary beam advancing toward the direction tilting fromthe Z-axis at an angle α (45°) The insertion of the reflector 104, inparticular, may provide an effective tilt angle according to theembodiment 1 of the present invention.

FIGS. 6A and 6B are the views showing the directivity of the antennadevice according to the embodiment 1 of the present invention. In FIG.6A, a directivity 401 indicates the directivity of ahorizontally-polarized wave (Eφ) component on a vertical (X-Y) plane. Asknown from this figure, the primary beam advances toward the direction,in which θ tilts at an angle of 45°.

In FIG. 6B, a directivity 402 indicates the directivity ofhorizontally-polarized wave (Eφ) component on a conical surface, ofwhich θ is 45°. As know from this figure, the primary beam advancesalong the X-axis and the half-width of the horizontal plane (a gain isan angle within −3 [dB] relative to its maximum gain) is 60°. In thiscase, the directivity of the primary beam may achieve a gain of 9.9[dB].

As aforementioned, according to the antenna device according to theembodiment 1 of the present invention, by placing the linear elementswith a length equivalent to half a wavelength so that they may draw adiamond shape and incorporating the delay elements at the opposite apexpairs, the antenna device suitably mounted on a small wireless apparatusmay be achieved and further, the primary beam of whichhorizontally-polarized wave has a tilt angle of 45°, may be formed.

Note that in the embodiment 1, which has been mentioned assuming thatthe distance h from the linear elements to the reflector is equivalentto 0.42 wavelength, by changing the distance h, the tilt angle α may bevaried. As the distance h is decreased, the tilt angle narrows and as itbeing increased, the tilt angle augments. Note that an increase indistance h may cause an unwanted maximum point (minor lobe) ofdirectivity to occur along the −X-axis. For this reason, by selectingthe distance h from a range of values from one fourth wavelength to halfa wavelength depending on the application of the antenna, the gain ofthe antenna may be improved. In the embodiment 1, h has been set to 0.42wavelength, achieving the optimal tilt angle and directivity.

In addition, in the embodiment 1, which has been mentioned assuming thatthe length of delay elements is equivalent to one fourth wavelength, bychanging the length of the delay elements, the tilt angle a may bevaried. As the length of the delay elements is decreased, the tilt anglenarrows and as the length being increased, the tilt angle widens. Notethat an increase in length of the delay elements may cause a minor lobeof directivity to occur along the −X-axis. For this reason, by selectingthe length of the delay elements of the antenna from a range of valuesfrom 0.2 to 0.35 wavelength depending on the application of the antenna,the gain of the antenna may be improved. In the embodiment 1, the lengthof the delay elements is set to one fourth wavelength, achieving theoptimal tilt angle and directivity.

Furthermore, in the embodiment 1, conductor type of delay lines areused, though the use of lumped constant parts, for example, inductors,may have the same effects as those aforementioned.

It goes without saying that although the linear elements, which havebeen placed so that they may draw a diamond shape, have been mentionedso far, the elements may be placed so that they may draw a square.

Moreover, in the embodiment 1, which has been mentioned using fourlinear elements, according to the present invention, two linear elementsare bent to form linear delay elements, enabling the diamond-shape withdelay elements to be achieved. This may not only have a less number ofparts compared with the antenna composed of four linear elements butalso make easy the process of manufacturing antennas.

Embodiment 2

FIG. 7 is a view showing the configuration of an antenna deviceaccording to the embodiment 2 of the present invention. Note that thesame portions in FIG. 7 as those in FIG. 3 have the symbols identical tothose in FIG. 3 to omit their detailed descriptions. Only one differencebetween FIGS. 3 and 7 is in that a director element 501 has been addedin the latter. The embodiment 2 is mentioned below assuming that theoperating frequency of the antenna is 5 GHz.

In FIG. 7, the director element 501 is a conductor having a length L5equivalent to 0.46 wavelength (27.6 mm) and a element width of 1 mm. Thedirect or element 501 is placed at a distance L6 (1 mm) from the tips ofthe linear elements 101 c are 101 d along the X-axis.

FIGS. 8A and 8B are views showing the directivity of the antenna deviceaccording to the embodiment 2 of the present invention. In FIG. 8A, adirectivity 601 indicates the directivity of the horizontally-polarizedwave (Eφ) component on the vertical (X-Z) plane. As known from thisfigure, θ of the primary beam tilts at an angle of 45°. In FIG. 8B, thedirectivity 602 indicates the directivity of the horizontally-polarizedwave (Eφ) component on the conical surface, of which θ is 45°. In thiscase, the directivity of the primary beam achieves a gain of 11.2 [dB].In this way, the incorporation of the director element 501 may convergea radiated beam along the X-axis, improving the gain of thediamond-shape antenna with delay elements along the X-axis. This meansthat simply by enlarging the dimension of the antenna device mentionedin the description of the embodiment 1 by only 2 mm, a 1.3 [dB] highergain may be achieved.

Thus, according to the antenna device according to the embodiment 2 ofthe present invention, the addition of the director element to theantenna device mentioned in the description of the embodiment 1 mayimprove the gain in the direction of the director element.

Note that the distance L6 between the director element 501 and thelinear elements 101 c or 101 d, and the length of the director length L5are given as only examples. By modifying these parameters to change boththe directivity and gain of the antenna device, appropriate parametersmay be selected depending on the application of the antenna.

Two or more director elements instead of only one element may beincorporated in a row along the X-axis to achieve a further higher gain.

Embodiment 3

In the embodiment 3, an antenna device, in which the linear elements ofthe antenna device mentioned in the embodiment 1 have been replaced withslot (gap) elements.

FIG. 9 is a view showing the configuration of the antenna deviceaccording to the embodiment 3 of the present invention. Note that thesame portions in FIG. 9 as those in FIG. 3 have the symbols identical tothose in FIG. 3 to omit their detailed descriptions. The embodiment 3 ismentioned below assuming that the operating frequency of antenna is 5GHz.

In FIG. 9, a substrate 701 is a dielectric with a dielectric constant εrof, for example, 2.6 and a thickness of 1.6 mm, wherein the effectivewavelength (λ_(e)) on the substrate 701 is equivalent to 84% of thewavelength (λ₀) in a free space. This means that a relationship may beestablished between both the wavelengths; λ_(e)=0.84λ₀. For this reason,the effective wavelength (λ_(e)) is used to explain the embodiment 3below. The length L11 of each side of the substrate 16 is equivalent to1.107λ_(e) (56 mm).

A copper foil layer 702 indicates the copper foil adhered to the side Zof the substrate 701. Slot elements 703 a to 703 d are the slotelements, which have been formed by denuding the cupper foil layer 702.Slot delay elements 704 a and 704 b are also formed by denuding thecupper foil layer 702. The length L7 of each of the slot elements 703 ato 703 d is set to ½λ_(e) (25 mm). The element length of each of thedelay elements 704 a and 704 b is ¼λ_(e) (12.6 mm) and the length L8 ofeach of their longitudinal sides is set to ⅛λ_(e) (6.3 mm).

A gap L10 with the cupper foil layer left, which is defined between thetips of the slot elements 703 c and 703 d, is 2 mm. A slot (gap) isconnected to the elements 703 a and 703 b.

A slot diamond-shape antenna with delay elements having a length L9equivalent to 0.702λ_(e) (35.4 mm) is composed of the slot elements 703a to 703 d and the slot delay elements 704 a and 704 b formed in theaforementioned way.

A micro strip line 705 is formed using the copper foil layer along theX-axis in the vicinity of the connection between the slot elements 703 aand 703 b on the −Z side on the substrate 701. The width W of the microstrip line 705 is 4.3 mm and its characteristic impedance is set to 50Ω. The distance L12 between the tip of the micro strip line 705 and theconnection between the slot elements 703 a and 703 b is set to, forexample, 4.5 mm.

This configuration enables the micro strip line 705 and the slotdiamond-shape antenna with delay elements are electro-magneticallycoupled to one another, allowing the micro strip line 705 to operate asa feeding line. This makes it possible to feed power with impedancesbalanced, resulting in easy power feed to the dielectric substrate fromthe micro strip line, a plane circuit. Thus, the antenna device may befurther miniaturized.

In the diamond-shape antenna with delay elements according theembodiment 3 shown in FIG. 9, the linear elements of the diamond-shapeantenna with delay elements shown in FIG. 3 have been replaced with theslot elements. The operating principle of the antenna may be explainedwith an electric field replaced with a magnetic field. Thus, the primarypolarized wave component of the slot diamond-shape antenna with delayelements shown in FIG. 3 is a horizontal component while that shown inFIG. 9 is vertical component (Eθ).

FIGS. 10A and 10B are views showing the directivity of the antennadevice according to the embodiment 3 of the present invention. In FIG.10A, a directivity 801 indicates the directivity of thevertically-polarized wave (Eθ) component on the vertical (X-Z) plane. Asknown from this figure, θ of the primary beam tilts at an angle of 35°.

In FIG. 10B, a directivity 802 indicates the directivity of thevertically-polarized wave (Eθ) component on the conical surface, ofwhich θ is 35. This means that the primary beam advances along theX-axis. It also may be confirmed that the half-width of the horizontalplane is 60°. The directivity of the primary beam may achieve a gain of10.6 [dB].

Thus, according to the antenna device according to the embodiment 3, notonly the antenna device, which may be suitably mounted on a smallwireless apparatus, may be provided but also the tilt angle of 35′ maybe used and the vertical polarized wave (Eθ) component is used as theprimary polarized wave component by placing the slot elements with alength equivalent to half a width so that they may draw a diamond shapeand incorporating the delay slot elements at the opposite apex pairs tomake the plane smaller.

Note that although in the embodiment 3, the slot elements have beenformed using the copper foil layer on the dielectric substrate, almostthe same effect may be achieved, for example, by forming the slots(gaps) on the conductor plate.

Embodiment 4

FIG. 11 is a view showing the configuration of an antenna deviceaccording to the embodiment 4 of the present invention. Note that thesame portions in FIG. 11 as those in FIG. 9 have the symbols identicalto those in FIG. 9 to omit their detailed descriptions. Only onedifference between FIGS. 9 and 11 is in that a director slot element 901has been added in the latter. The embodiment 4 is explained belowassuming that the operating frequency of the antenna is 5 GHz.

In FIG. 11, the director slot element 901 is the slot with a length L13equivalent to 0.4λ_(e) (20.4 mm) and an element width of 1 mm. Thedirector slot element 901 is placed at a L14 (2 mm) distance from thetips of the slot elements 703 c and 703 d along the X-axis in parallelto the Y-axis. Note that λ_(e) is assumed to be 0.84λ.

Thus, since the formation of the director slot element 901 enables thebeam radiated from the slot diamond-shape antenna with delay elements toconverge along the X-axis, improving the ratio (F/B ratio) between thegains along the X and −X axes.

FIGS. 12A and 12B are views showing the directivity of the antennadevice of according to the embodiment 4 of the present invention. InFIG. 12A, the directivity 1001 indicates the directivity of thevertically-polarizes wave (Eθ) component on the vertical (XZ) plane.From this figure, the primary beam, of which θ tilts at an angle of 45°may be recognized. In FIG. 12B, the directivity 1002 indicates thedirectivity of the vertically-polarizes wave (Eθ) component on theconical surface at an angle of 45°.

As known from FIG. 12, the formation of the director slot element 901enables the tilt angle to be enlarged up to 40° and the F/B ratio of 12[dB] to be achieved.

Thus, according to the antenna device according to the embodiment of thepresent invention, the formation of the director slot element on theantenna device mentioned in the embodiment 3 enables the tilt angle tobe enlarged and higher F/B ratio to be achieved.

Note that the distance L14 between the director slot element 901 and theslot elements 703 c and 703 d, as well as the length L13 of the directorslot element 901, are just examples taken in describing this embodiment.It is preferable to select appropriate parameters according toindividual applications because the directivity and gain of the antennamay change as these parameters are modified.

In addition, more than one director slot element(s) may be used. Rather,two or more of the director slot elements aligned in line along the Xaxis would offer further higher F/B ratio.

Embodiment 5

FIG. 13 is a view showing the configuration of an antenna deviceaccording to an embodiment 5 of the present invention. The antennadevice shown in this figure has six slot diamond-shape antennas withdelay elements linearly placed shown in FIG. 9.

In FIG. 13, each of the slot diamond-shape antennas with delay elements101 a to 1101 f has the same configurationas that of the antenna deviceshown in FIG. 9. The antennas 101 a to 101 f are placed while beingrotated so that their primary beams (indicated by arrows in the figure)may divide 360° into six sectors on the horizontal plane and may beshifted by 60° each other.

The outer dimension of the six-sector antenna shown in FIG. 13 is L15 of36.3 mm (0.61 wavelength), L16 of 218.4 mm (3.64 wavelength), and anarea of 7993 mm². This area is equivalent to one forth of the area(30790 mm₂) of conventional six-sector antenna, indicating that the sizeof the antenna has been significantly reduced.

In the case where the operating frequency of the antenna is 25 GHz, theshape of the six-sector antenna shown in FIG. 13 is rectangular (7.3mm×43.7 mm), namely the shape and size of the six-sector antenna shownin FIG. 13 allows the antenna to be suitably mounted on any of smallwireless apparatuses, for example, a notebook-PC type.

FIG. 14 is a view showing the directivity of the antenna according tothe embodiment 5 of the present invention. In the figure, directivities1201 a to 1201 f of the vertically-polarized wave (Eθ) components of theslot diamond-shape antennas 1101 a to 1101 f with delay elements on theconical surface are shown.

As known from FIG. 14, the directivities have been formed in thedirections, which are shifted by 60°, on the horizontal (X-) plane. Atthe middle point between two adjacent sectors (for example, in thedirection at an angle of 30°), only the minimum gain can be achieved butit is still just −3 [dB] less than that of the maximum gain in thisdirection. This means that higher gains may be achieved in all theradial directions.

By selectively feeding power to the slot diamond-shape antennas withdelay elements 101 a to 101 f configured as aforementioned, switchingmay be achieved among the sectors obtained by dividing 360° on thehorizontal plane by six. This provides the six-sector antenna.

Thus, according to the embodiment 5 of the present invention, by placingsix slot diamond-shape antennas with the delay elements on therectangular plane while rotating them by 60° and selectively feedingpower to the antennas, higher gains may be achieved in all the radialdirections, providing a small six-sector antenna.

Note that in the embodiment 5, the method for achieving the six-sectorantenna has been mentioned but the present invention is not limited tothis type of antennas and may be applicable to the method formanufacturing a plurality of sector antennas.

Although in the embodiment 5, the antenna device shown in the embodiment3 has been mentioned, the antenna device described in any otherembodiment may be used.

The antenna device of the present invention comprises four linearelements, each of which has a length equivalent to a half wavelength ofan operating frequency, the elements being placed so that they may drawa diamond shape on a plane, a feeding section that feeds power to oneend of a first linear element and one end of a second linear element,the section being put at one of the apexes of a diamond shape, a firstdelay section connected to the other end of the first linear element andone end of a third linear element for delaying the phase of an antennacurrent by a given phase, a second delay section connected to the otherend of the second linear element and one end of a fourth linear elementfor delaying the phase of an antenna current by the same phase as thatof the first delay section, and a reflector placed at a given distancein parallel to a plane, on which the linear elements have been placed.

Since according to this configuration, the phases of the antennacurrents are delayed by the given phase component by means of the firstdelay means and the second delay means, the phases are shifted betweenthe antenna currents flowing on the first and second linear elements andbetween the antenna currents flowing on the second and fourth linearelements. This composes an electric wave radiated and an electric wavereflected at the reflector, achieving the antenna device capable offorming the primary beam tilting toward the horizontal place.

In the aforementioned configuration of the antenna device of the presentinvention, the first delay section and the second delay section have alength within a given range, the sections being linear elements having abent form.

According to this configuration, by changing the length of the bentlinear elements to any other one within the given limits, the amount ofdelayed phase component of the antenna current may be varied, resultingin a tilt angle modified to a desired one.

In the aforementioned configuration of the antenna device of the presentinvention, the first delay means and the second delay means are lumpedconstant parts.

According to this configuration, by changing the lumped constant of thelumped constant parts to any other one, the amount of delayed phasecomponent of the antenna current may be varied, resulting in a tiltangle modified to a desired one.

The aforementioned configuration of the antenna device of the presentinvention comprises: at least one director element having a lengthequivalent to a half wavelength or less, the director element beingplaced at a given distance from an open end of the linear element.

According to this configuration, the radio wave radiated from thediamond-shape antenna device may be converged toward the directorelement, improving the gain in the direction of the director element.

The antenna device of the present invention comprises two linearelements having the same length, a bending part formed by bending thetwo linear elements at the centers of the elements with a length withina given range, a feeding section connected to one end of the two linearelements to feed power, and the reflector placed at a given distance inparallel to a plane containing the two linear elements, wherein the twolinear elements are bent and placed so that they draw a diamond shape,of which one side has a length equivalent to a half wavelength of anoperating frequency and the other ends of the two linear elements areopen.

According to this configuration, by inserting two bent linear elements,the diamond-shape with delay elements may be formed, enabling theantenna device to be assembled using less number of parts. This makeseasy the process of manufacturing antenna devices.

The antenna device comprises a dielectric substrate with a givendielectric constant,

a conductor layer formed on the dielectric substrate,

a diamond-shape slot element formed on the conductor substrate, of whicheach side has a length equivalent to a half wavelength of an operatingfrequency,

the first delay section and the second delay section, which have beenplaced at each of opposite apex pairs of the diamond shape to delay thephase of an antenna current,

the feeding section, which have been placed on either of another one ofthe opposite apex pairs of the diamond shape, for feeding power to theslot elements,

a termination part formed at the other of another one of the oppositeapex pairs of the diamond shape, for terminating the slot elements, and

the reflector placed beyond the substrate at a given distance from andin parallel to the conductor layer.

Since according to this configuration, the delay means delay the phasesof the antenna currents, the phases may be out of phase between theantenna currents flowing through the slot element from the feeding meansto the delay means and flowing through the slot element from the delaymeans to termination part. This composes the electric wave radiated andthe electric wave reflected at the reflector, achieving the antennadevice, which may form the primary beam, of which vertically-polarizedwave tilts toward the horizontal plane.

In the aforementioned configuration of the antenna device of the presentinvention, the first delay section and the second delay section are theslot elements having a bent form with a length within the given range,which are formed on the conductor layer.

Since according to this configuration, by changing the length of each ofthe bent slot elements to any other one within the given limits, theamount of the delayed phase component of the antenna current, resultingin the modified tilt angle. This brings the desired tilt angle.

In the aforementioned configuration of the antenna device of the presentinvention, the feeding section feeds power using a micro strip line laidon a rear plane of the substrate, on which the conductor layer has beenformed.

According to this configuration, the feeding means may feed power to theslot elements with impedances well-balanced, providing not only easierpower feed but also a further miniaturized antenna device.

In the aforementioned configuration of the antenna device of the presentinvention, at least one director slot element with a length equivalentto a half wavelength or less, which has been formed at a given distancefrom the termination part of the slot element.

According to this configuration, the radio wave radiated from thediamond-shape antenna device may be converged toward the directorelement, improving the gain in the direction of the director element.

The sector antenna of the present invention has been configured so thata plurality of antenna devices according to claim 1 are used, theantenna devices being placed on a plane while being shifted at equalangle from each other.

According to this configuration, the sector antenna capable of formingthe primary beam advancing toward the desired direction may be achieved.

In the aforementioned configuration of the sector antenna of the presentinvention, six antenna devices have been placed in a row on a givenrectangular plane, the six antenna devices being shifted by 60° fromeach other.

According to this configuration, by rotating the diamond-shape sixantenna devices by 60° relative to adjacent ones when being placed onthe rectangular place, a six-sector antenna capable of forming theprimary beams advancing toward six different directions at an equalinterval may be obtained, achieving a sector antenna suitably mounted onany of small wireless apparatuses.

As aforementioned, according to the present invention, the open-enddiamond-shape antenna, of which one side has a length equivalent to halfa wavelength, wherein the delay elements are placed at each of theopposite apex pairs and a reflector is inserted at a given distance inparallel to the plane, in which the elements are place, may form theprimary beam, of which horizontally-polarized or vertically-polarizedwave tilts toward the horizontal plane. In addition, the diamond-shapeantennas with delay elements may be rotated at an even angle when beingplaced on the rectangular plane, achieving a sector antenna suitablymounted on any of small wireless apparatuses.

This specification was prepared based on the patent application No.2003-022369 filed on Jan. 30, 2003. This statement is specificallycontained here.

INDUSTRIAL APPLICABILITY

The present invention may be suitably applied to fixed wirelessapparatuses and wireless terminals configured in a wireless LAN system.

1. An antenna device having an open end, comprising: four linearelements, each of which has a length equivalent to a half wavelength ofan operating frequency, the elements being placed so that they may drawa diamond shape on a plane, a feeding section that feeds power to oneend of a first linear element and one end of a second linear element,the section being put at one of the apexes of a diamond shape, a firstdelay section connected to the other end of the first linear element andone end of a third linear element for delaying the phase of an antennacurrent by a given phase, a second delay section connected to the otherend of the second linear element and one end of a fourth linear elementfor delaying the phase of an antenna current by the same phase as thatof the first delay section, and a reflector placed at a given distancein parallel to a plane, on which the linear elements have been placed.2. The antenna device according to claim 1, wherein the first delaysection and the second delay section have a length within a given range,the sections being linear elements having a bent form.
 3. The antennadevice according to claim 1, wherein the first delay section and thesecond delay section are lumped constant parts.
 4. The antenna deviceaccording to claim 1, comprising: at least one director element having alength equivalent to a half wavelength or less, the director elementbeing placed at a given distance from an open end of the linear element.5. An antenna device, comprising: two linear elements having the samelength, a bending part formed by bending the two linear elements at thecenters of the elements with a length within a given range, a feedingsection connected to one end of the two linear elements to feed power,and the reflector placed at a given distance in parallel to a planecontaining the two linear elements, wherein the two linear elements arebent and placed so that they draw a diamond shape, of which one side hasa length equivalent to a half wavelength of an operating frequency andthe other ends of the two linear elements are open.
 6. An antenna devicecomprising: a dielectric substrate with a given dielectric constant, aconductor layer formed on the dielectric substrate, a diamond-shape slotelement formed on the conductor substrate, of which each side has alength equivalent to a half wavelength of an operating frequency, thefirst delay section and the second delay section, which have been placedat each of opposite apex pairs of the diamond shape to delay the phaseof an antenna current, the feeding section, which have been placed oneither of another one of the opposite apex pairs of the diamond shape,for feeding power to the slot elements, a termination part formed at theother of another one of the opposite apex pairs of the diamond shape,for terminating the slot elements, and the reflector placed beyond thesubstrate at a given distance from and in parallel to the conductorlayer.
 7. The antenna device according to claim 6, wherein the firstdelay section and the second delay section are the slot elements havinga bent form with a length within the given range, which are formed onthe conductor layer.
 8. The antenna device according to claim 6, whereinthe feeding section feeds power using a micro strip line laid on a rearplane of the substrate, on which the conductor layer has been formed. 9.The antenna device according to claim 6 comprising: at least onedirector slot element with a length equivalent to a half wavelength orless, which has been formed at a given distance from the terminationpart of the slot element.
 10. A sector antenna device, wherein aplurality of antenna devices according to claim 1 are used, the antennadevices being placed on a plane while being shifted at equal angle fromeach other.
 11. The antenna device according to claim 10, wherein sixantenna devices have been placed in a row on a given rectangular plane,the six antenna devices being shifted by 60° from each other.